Intramedullary nails have found widespread use in osteosynthesis. Since the first application of this method by KUNTSCHER, intramedullary nails have been developed to include a wide range of indications (locking, gamma nail, reconstruction nail).
Despite the wide range of development, the basic concept has remained unchanged. It involves introducing a hollow or solid cylinder into the intramedullary cavity of a tubular bone. In early days nailing of the femur was predominant, but with time this type of osteosynthesis has been applied to all major long bones. Because the intramedullary canals of the various long bones have been prepared by reaming out the medullae with reamers no particular attention has been paid to nail configuration or profile.
Conventional intramedullary nails are typically rigid, stiff and relatively straight. As a result, the insertion points of the nail into the bone are usually fixed and are determined by the geometries of the nail and the medullary canal. However the points selected for insertions of rigid intramedullary nails may have drawbacks for reasons of anatomy and accessibility:
significant muscle coverage over insertion site may make the insertion point difficult to approach surgically and may, as well, lead to soft tissue damage as the surgeon tries to approach the insertion site; PA1 possible interference with joint areas PA1 possible damage to the opposite cortex caused upon entry of the rigid nail tip into the medullary canal; PA1 risk of damage to bone at the insertion site due to excess stress during insertion of nail (caused by too rigid nails); PA1 the insertion site and nail path created by a rigid intramedullary nail in a long bone may interfere with the growth plate in your patients. PA1 The insertion point is not fixed and can be chosen according to anatomical factors so as to avoid soft tissue damage and interference with joints and growth plates; PA1 anterograde and retrograde approach may both be possible; PA1 there is less risk of damage to the bone at the insertion point and at the inner cortex during insertion; PA1 it may be used on young patients by simply avoiding the growth plates during introduction and insertion of the nail into the medullary cavity.
An intramedullary nail having a flexible conformation which can be stiffened after insertion of the nail into the medullary cavity is disclosed in SU 1111-748-A. The drawback of this nail lies in the fact that its single segment has end teeth and knurled surfaces forming pairs of locking joints so that upon stiffening the nail takes on the shape of the intramedullary cavity irrespective of the possible presence of a displaced fracture.
Another aspect is the geometry of the nail cross section. If one is concerned with causing the least damage to the intramedullary cavity and preserving blood circulation in the bone, the nail cross section has to be taken into consideration more seriously. This is particularly true for the nailing of the humerus. The intramedullary cavity of the humerus is not circular over its entire length, and therefore the axially off-set insertion of a nail with a circular profile is not recommended.